Towards Low NOx Emissions Performance of a 65kW Recuperated Gas Turbine Operated on 100% Hydrogen

Abstract This work supports the development of a low NOx emission 65 kW natural gas turbine capable of operating on 100% hydrogen. This gas turbine has been demonstrated to operate from cold start to full load on up to 30% hydrogen mixed into natural gas with single digit ppm NOx emissions. To reach operation on 100% hydrogen, injectors specifically designed to 1) avoid challenges with flashback and 2) be field retrofittable were developed and tested. The injectors must be designed to prevent flashback while having a high degree of mixing coupled with fuel lean operation to achieve desired low NOx emissions. Successful operation of the engine from cold start to full load on 100% hydrogen was demonstrated. With the successful demonstration of operability, the new injectors serve as a starting point to improve the turbine performance and emissions when operated on hydrogen. To support the development, a chemical reactor network (CRN) is used in conjunction with experimental injector mixing characterization. The CRN analysis predicts NOx using perfectly stirred reactors (PSR). A strategy to account for variation in mixing performance was developed and utilized with the CRN to connect NOx emissions to the injector mixing performance. Fuel concentration profiles produced by different injector designs were measured and the CRN model was used to infer the effects on NOx emission. The CRN model was validated/tuned using measured NOx emissions data from two combustion liners and two injector designs and the corresponding measured injector fuel distributions. The results illustrate how NOx emissions are directly influenced by local fuel rich regions found at the injector outlet. The CRN model can thus be used to screen injector designs and infer NOx performance and will be used to guide the development of injectors for hydrogen that can attain desired fuel distributions, concentrations, and velocities. The results affirm the direction needed to attain improved mixing and to operate at overall leaner conditions made possible by the stabilizing features inherent to hydrogen.